This invention relates to printed circuit board assemblies in which a base board supports at least one additional circuit board, referred to as a mezzanine board or a daughter board. More specifically, the invention relates to the way the mezzanine board is mounted to the base board, and the ability to insert or remove mezzanine boards while the supporting base board and adjacently mounted base boards and mezzanine boards remain in service.
The general use of daughter boards supported by a base board is well established. For example, the motherboard of a personal computer typically accepts a plurality of daughter boards that plug into sockets on the motherboard so that the daughter boards are mounted perpendicular to the motherboard. This arrangement promotes configurability and flexibility since different daughter boards that provide different functions can be selected for use with a motherboard.
Mezzanine boards have also been used to provide similar configurability. As used herein, a xe2x80x9cmezzanine boardxe2x80x9d refers to a circuit board that is mounted co-planar to its associated base board. In known arrangements rigid, cylindrical standoffs mount the mezzanine board to the base board. Typically, screws are used to secure the mezzanine board to the standoffs.
While this mounting arrangement of mezzanine boards provides configurability, such mezzanine boards cannot be hot-swapped, that is, the mounting arrangement prevents the removal or installation of a mezzanine board while its supporting base board remains installed and in active electrical operation. This problem is exacerbated where a plurality of base boards are mounted in adjacent slots in a shelf, such as designed for mounting in a rack. The presence of another adjacent base board in close proximity to the mezzanine board prevents access to the screws located at the standoff locations on the mezzanine board. Thus, to remove or install a mezzanine board on a shelf-mounted base board, the base board has to be taken out of electrical service and removed from its slot in the shelf. This is generally undesirable and is especially disadvantageous in equipment, such as in telecommunication networks, where continuous service must be provided.
The above problem is solved and an advance made in the art in accordance with the present invention that accommodates the insertion or removal of a mezzanine board while the supporting base board remains in service. As used herein, a board being xe2x80x9cin servicexe2x80x9d means that it is in its normally installed position and is operating to provide intended functions.
It is an object of the present invention to provide an improved mounting technique by which mezzanine boards can be inserted or removed from the supporting base board while the base board remains in active electrical service. The mounting technique also supports this functionality even while the supporting base board is mounted in a shelf with other base boards in adjacent slots. It is a further object of the invention to accommodate different widths of mezzanine boards.
In accordance with an embodiment of the present invention, an assembly of circuit boards includes a base board and a faceplate mounted along the edge of the base board. Spaced apart mounts are attached to the base board. Guide rails are attached to the base board by the mounts and extend away from the plane of the base board. The guide rails include at least one longitudinal channel. The channels on two guide rails engage opposing edges of a mezzanine board and permit the mezzanine board to be slid into position and supported. The faceplate includes an aperture dimensioned to accept the mezzanine board so that the mezzanine board can be installed or removed while the base board remains in active electrical service.